Karlie Kloss is engaged to Joshua Kushner, will be future sister-in-law of Ivanka Trump

The 25-year-old supermodel, and BFF to pop star Taylor Swift, confirmed her engagement to venture capitalist and New York real estate investor Joshua Kushner, 33, after six years of dating, in a sweet post to social media on Wednesday.

"I love you more than I have words to express," she captioned the snuggly sunset pic of herself and Kushner. "Josh, you're my best friend and my soulmate. I can't wait for forever together. Yes a million times over 💍"

Kushner responded by sharing an ethereal photo of his bride-to-be and captioning it: "Fiancée"

Kloss also shared a quick peek at her massive sparkler on her Instagram Story.

(Instagram)

A source close to Kloss told People that Kushner "proposed a few weeks ago during a romantic weekend together in upstate New York."

"They're both overjoyed and happily celebrating," the source added. "Their hearts are full and they're excited to build their future together."

A source also told the publication that Kloss converted to Judaism in early June.

"She's never been one to make decisions lightly,” the source said. "She spends a lot of time reflecting and learning."

Karlie Kloss and Joshua Kushner in 2016. (Getty)

Kloss and Kushner have kept their relationship relatively private, only occasionally sharing photos of each other on social media.

Kushner is the younger brother of Jared Kushner, senior advisor to US President Donald Trump. Jared is married to Trump's daughter Ivanka.

Joshua has previously described himself as a "lifelong Democrat" and said through a spokesperson in 2016 that he didn't plan to vote for Trump in the US presidential election. We would imagine this might have caused some interesting debate in the Kushner-Trump household, given the Trump family's staunch conservative values.

Kloss herself has been an advocate for women's empowerment, having founded Kode with Klossy, a free, two-week coding summer program for girls aged 13-18, in 2012. It's through her work with Klossy that the supermodel met her husband-to-be.